1. Field of the Invention
This invention relates to improvements in a fluid jet loom, and more particularly to a weft picking system including a roller type weft traction device between a weft measuring and storing device and a fluid jet nozzle to draw a weft yarn at a high speed toward the fluid let nozzle.
2. Description of the Prior Art
Fluid jet looms are provided with a weft picking system which is arranged to accomplish a weft picking under the influence of a fluid jet ejected from a nozzle or nozzles. The weft picking system accomplishes weft picking at a high speed with the fluid jet, and therefore is highly advantageous from the view point of improving productivity of a fabric and availability of the loom. However, for example, in case of accomplishing the weft picking under the influence of an air jet, a weft yarn is pulled and flown under a frictional force between the air stream and the weft yarn, and therefore such a weft picking consumes a large amount of pressurized air consumption (or electric power), thus being problematic from an energy consumption viewpoint.
In view of the above, a weft picking system has been proposed to deal with the above energy consumption problem as disclosed, for example, in Japanese Patent Provisional Publication No. 57-199841. In this publication, a pair of rotating rollers are provided to be contactable and separable, in which a weft yarn is held between and drawn by the rollers particularly at the initial stage of a weft picking period at which pressurized air consumption is particularly high, thereby saving the air consumption.
Thus, although the above-discussed conventional weft picking system is considerably effective from the viewpoint of reducing energy consumption because a fluid jet nozzle is used only for regulating the weft yarn to be picked under the direct traction by the rollers, a variety of drawbacks have been encountered in the conventional weft picking system as discussed below.
That is, for example, in the case where a weft reaching sensor detects a short pick in the course of the weft picking, a controller immediately outputs a loom stop signal to stop the operation of the loom. If the operation of the loom which is making its high speed revolution is suddenly stopped, a strong shock is applied onto a reed and onto a shedding mechanism, providing problems in durability of the loom. In this regard, stopping of the loom operation is made at the weft picking timing in the next weaving cycle upon completion of the beating-up operation with the reed. Thus, although the revolution of the loom is continued to the next weft picking timing when the loom is stopped, unwinding of the weft yarn from a weft measuring and storing device can be prevented to disable the next weft picking from being made in order to facilitate removal of the failed or shortpicked weft yarn.
At this time, the unwinding of the weft yarn is stopped in a condition of being kept between the rollers which still continue to rotate at a high speed by inertia, and therefore the weft yarn is unavoidably drawn by the rollers though the weft yarn is not unwound from the weft measuring and storing device. This unavoidably causes breakage of the weft yarn. It seems that the above problem can be solved by braking the rotating rollers. However, the weft traction device is required to be small-sized and therefore has rollers which are smaller in outer diameter. Additionally, the rollers are required to rotate at high speeds in case the loom is operated or revolved at high speeds. In view of these, in order to stop the rollers abruptly at a suitable timing, a braking device high in response and in braking force is required. This also causes problems in durability of the rollers and the braking device. Thus, it has been impossible to securely and abruptly stop the rotating rollers, thereby leaving the above problems unsolved.
In addition to the above case of failure in weft picking, the loom is required to be stopped, for example, for restoring breakage of a weft yarn and for periodic maintenance of the loom. In such a case, if the loom is stopped in a condition where the weft yarn is held between the rotating rollers, breakage of the weft yarn unavoidably occurs in the manner discussed above. Furthermore, in a condition where the weft yarn is held between the rollers, the weft yarn is being restrained by the rollers and therefore becomes a hindrance to the removal operation for the failed weft yarn and to the maintenance operation of the loom thereby degrading the operability of the loom.